Re: [PATCH 2/8] fwctl: Basic ioctl dispatch for the character device

Leon Romanovsky
2024-06-04T12:22:27Z

On Tue, Jun 04, 2024 at 02:16:12PM +0200, Zhu Yanjun wrote:
> On 03.06.24 17:53, Jason Gunthorpe wrote:
> > Each file descriptor gets a chunk of per-FD driver specific context that
> > allows the driver to attach a device specific struct to. The core code
> > takes care of the memory lifetime for this structure.
> >
> > The ioctl dispatch and design is based on what was built for iommufd. The
> > ioctls have a struct which has a combined in/out behavior with a typical
> > 'zero pad' scheme for future extension and backwards compatibility.
> >
> > Like iommufd some shared logic does most of the ioctl marshalling and
> > compatibility work and tables diatches to some function pointers for
> > each unique iotcl.
> >
> > This approach has proven to work quite well in the iommufd and rdma
> > subsystems.
> >
> > Allocate an ioctl number space for the subsystem.
> >
> > Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> > ---
> > .../userspace-api/ioctl/ioctl-number.rst | 1 +
> > MAINTAINERS | 1 +
> > drivers/fwctl/main.c | 124 +++++++++++++++++-
> > include/linux/fwctl.h | 31 +++++
> > include/uapi/fwctl/fwctl.h | 41 ++++++
> > 5 files changed, 196 insertions(+), 2 deletions(-)
> > create mode 100644 include/uapi/fwctl/fwctl.h

<...>

> > static int fwctl_fops_open(struct inode *inode, struct file *filp)
> > {
> > struct fwctl_device *fwctl =
> > container_of(inode->i_cdev, struct fwctl_device, cdev);
> > + struct fwctl_uctx *uctx __free(kfree) = NULL;
> > + int ret;
> > +
> > + guard(rwsem_read)(&fwctl->registration_lock);
> > + if (!fwctl->ops)
> > + return -ENODEV;
> > +
> > + uctx = kzalloc(fwctl->ops->uctx_size, GFP_KERNEL | GFP_KERNEL_ACCOUNT);
> > + if (!uctx)
> > + return -ENOMEM;
> > +
> > + uctx->fwctl = fwctl;
> > + ret = fwctl->ops->open_uctx(uctx);
> > + if (ret)
> > + return ret;
>
> When something is wrong, uctx is freed in "fwctl->ops->open_uctx(uctx);"?
>
> If not, the allocated memory uctx leaks here.

See how uctx is declared:
struct fwctl_uctx *uctx __free(kfree) = NULL;

It will be released automatically.
See include/linux/cleanup.h for more details.

Thanks